Video endoscopes and laparoscopes have been in general use since the 1980s. Laparoscopes are rigid devices that may be used in minimally invasive surgery. Typically, laparoscopes use a proximal, externally mounted hand piece that includes a digital camera. The digital camera collects video images through a series of rod lenses arrayed end-to-end inside a tube that extends into a body cavity of the patient. The camera returns its signal through wires to a console that often includes a display monitor. Also typically mounted on the console is a light source, often based on a xenon lamp. The light source sends light to the hand piece through an optical fiber, where a coupling is made. The light is then sent into the body cavity through optical fibers that run inside the laparoscope tube. Often, the optical fibers terminate at the distal end of the tube in a concentric ring, or partial arc around the periphery of the tube. In use, the illumination power is adjusted to give an image of appropriate brightness on the video monitor.
Endoscopes are typically flexible devices that may be used in diagnostic or other procedures. Modern endoscopes (and some laparoscopes) use a distal tip digital camera that collects light, converts it to an electronic signal, and sends the electronic signal up the flexible tube to a hand piece. The signal is then sent to a console for display similar to the manner of operation of laparoscopes. Illumination is sent to the body cavity in a manner similar to that of laparoscopes, except the illumination fibers typically terminate as a pair of apertures on each side of the camera lens. Endoscopes often include irrigation channels and working channels for instruments, in addition to a steering apparatus that may be used to aim the tip of the endoscope in the direction the clinician wishes to look or push the tube.
Endoscopes and laparoscopes may be end-looking or side-looking. In end-looking devices, the field-of-view is positioned directly in front of the end of the device. Side-looking devices may have their fields-of-view located 70°, or other angle off-axis from the end of the tube. The field-of-view varies according to the application. For instance, colonoscopes (a type of endoscope used to examine the colon) often have a 140° diagonal field-of-view, while laparoscopes may have fields-of-view closer to 70° diagonal.
Instruments may be passed down the working channel of many endoscopes. Forceps and other devices have been developed that may pass within the diameter of the working channel into the body cavity where the clinician uses them to take tissue samples, etc. In the field of laparoscopy, instruments are generally introduced to the procedure through separate small incisions. Often the instruments as well as the laparoscope pass through trocars, or rings that line the incisions to prevent undue binding or damage as well as maintain a seal.
Both laparoscopes and endoscopes may use a pixelated sensor array such as a charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) device. In pixelated imagers, each pixel corresponds to an element of an array and each element receives light energy from a conjugate point in the field-of-view for a selected sampling interval. Each element converts light to an electrical signal proportional to the brightness of its conjugate point.
Today's digital endoscopes and laparoscopes may suffer from limited image quality and dynamic range and often exhibit other undesirable artifacts. In the case of distal imaging systems in particular, diameter limitations have been a common hindrance to higher resolution.